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Wednesday, October 21, 2015

Pelvic Floor Muscle Activation and Strength Components

Helena Luginbuehl, et al, Neurourology and Urodynamics 34:498–506 (2015)

Elizabeth Lewis, PT, OCS, WCS
Oct. 14, 2015
Pelvic Physical Therapy Distance Journal Club
Description: This systematic review had a stated purpose of developing a better understanding of PFM activation and strength components in order to develop more specific PFM training regimens for female SUI patients.  The aim of this systematic review was to summarize/evaluate existing studies investigating PFM activation/strength components which influence female continence and SUI.

Introduction:
PFM- training for SUI is effective and so is recommended as a first line of therapy.  However, the optimal training regimen for achieving continence is still unknown. There is a question among caregivers of optimal PFM training protocols.  There is high variability in PFM training protocols.  A Cochrane review showed insufficient evidence (due to heterogeneity) to make any strong recommendations about the best approach to PFM training (in terms of supervision and content of programs).  Although specific training methods and principles have been well described in the rehab/training literature, PFM training needs to include them to improve maximal strength, power, hypertrophy, strength-endurance and related muscle action forms.  Also,  PFM training should also include periodization, which specifies optimum frequency, intensity and type of contraction during training sessions. An understanding of PFM activation in terms of the neuromuscular dimension is also necessary.
Methods: They used PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines and published their a priori protocol in PROSPERO (register of SR reviews in health and social work).    This was a systematic review vs. a meta-analysis because of the high heterogeneity of the data.   The search strategy included strength and activation related terms (such as muscle strength, force development rate and power), clinical condition of SUI, terms assoc. with PFM and measurement methods such as EMG, pressure, force, etc.  Studies reviewed were in English, French, Dutch and German (due to reviewers).
 (A systematic review comprehensively searches all related studies on a topic with a goal of reducing bias by identifying, appraising and synthesizing all relevant studies of a particular topic.  A systematic review can include a meta-analysis: which uses statistical techniques to synthesize data from several studies into a single quantitative estimate or summary of effect size.  A narrative review vs. a systematic review is based on availability or author selection of studies and so can have the risk of selection bias.) Information taken from internet, not from this study.
Search Strategy: They did a systematic search of the literature from January, 1980- November of 2013 in Pub Med, EMBASE and Cochrane databases for cross-sectional studies comparing female SUI patients with healthy controls and interventional studies of female SUI patients, looking at the association between PFM strength and activation and urine loss. Their search terms included terms for strength/activation, terms associated with the muscle nomenclature, clinical condition (SUI) and measurements methods such as pressure or EMG.
Inclusion and exclusion criteria were listed in Table 1, looking at Population: Female adults, with SUI stage 1-3, 1 yr PP, parous, nulliparous, pre- and post- menopausal, Interventions/exposures: EMG and or strength-measurements of PFM components with various electrodes and probes, Comparator: a) Healthy controls b) SUI patients pre and post PFM therapy . 
Main Outcomes:  a) Cross sectional studies reviewed: Association /no association between CON/SUI  and specific PFM components of women with SUI vs healthy controls  and b)  Pre and Post studies reviewed Association/no association between CON/SUI and specific PFM components  of women with SUI before/after PFM therapy.
They looked at PFM components, definitions, measurement methods, study outcomes and quality measures independently extracted based on the Cochrane risk of bias tool
Results: Selection of studies went from 2, 630 abstracts to fourteen (see article).  Nine studies were cross sectional, comparing SUI with healthy controls and five were clinical trials or intervention studies, (non-controlled pre-post design on females with SUI).  Two cross-sectional studies were looking at the same sample with different questions and two were investigating a vaginal probe, regarding the physics and clinical data.
Table 3 shows the cross sectional studies and their characteristics.  Measurement methods varied: Six studies measured strength with varied terminology including force or pressure and measured in Newtons or mmH20.  Three studies used EMG amplitude with varying probes.  Measured PFM components and their definitions were highly heterogeneous.
 Risk of Bias is in Table 2 and include (“+” here means succeeded to attain a low risk of bias) : (Summarizing for all nine studies), random sequence generation (selection bias) + in 2 studies(low risk of bias in 2 studies) , Allocation concealed (selection bias), + in 9 studies, Blinding of participants (not possible) and personnel (performance bias) + in 2 studies, Binding of Outcome assessment (detection bias), + in one study,  Incomplete outcome data ( attrition bias) + in 5 studies, Selective reporting (reporting bias) + in all studies and, Other sources of bias (+ in one study).
Table 4 summarizes the major characteristics of the five pre and post studies.  All studies used PFMT and two were secondary data analyses and one also used IFES.  The PFMT protocols and the measurement methods varied widely.  All studies measured strength, (terminology was strength, force or pressure).  Probes varied but were well established devices.  Changes in SUI were assessed with pad tests (varied) among other methods and all studies showed an improvement of the SUI   component measured and decreased urine loss after intervention.
Again, pooling of data for meta-analysis wasn’t possible due to high heterogeneity.
Discussion: Higher maximal, mean, endured and increase of PFM strength and earlier onset PFM activation were positively associated with female continence.  However, studies are heterogeneous in terms of methodology and terminology as well as definitions of the PFM activation and strength components and their characteristics.  Unclear terminology, test instructions and applications were applied, such as EMG measures not normalizing raw EMG data to compare independent groups (continent, SUI).  This, in addition to lack of information on the exact interventions given and the lack standardization of each intervention, limits the comparison of outcomes among the studies.
Strengths: First comprehensive systematic review on the topic of PFM activation and strength components influencing female continence and SUI.  They had a strong interdisciplinary team to do the literature review.
Weaknesses: Small number of trials and subjects, heterogeneity of terminology, test procedures and outcomes, so they couldn’t do a meta-analysis.  Subject ages varied widely, from 30—60 but didn’t include women over 70 (they said: a large group with SUI missed).
Conclusion: Noting the limitation of high methodological variability across these studies, this study suggests that PFM strength and activation components are associated with Female continence and SUI and generally supports the import of PFM training because improvements in PFM function may be related to improvement in SUI symptoms.  But it’s difficult to get a clear cut picture of SUI mechanisms.
They recommend more detailed knowledge about physiological and pathophysiological function of the PFM in terms of activation and strength (such as muscle metabolism, muscle action forms, sensorimotor and muscle fiber recruitment behavior, inhibition, voluntary/non-voluntary contractions, maximal strength, rate of force development and all combined.
PFM function has to be clarified for functional movements with SUI provoking impacts such as running, coughing, etc.  and not only in non- functional test conditions (MVC in supine).
Specific PFM training protocols could be developed on the basis of findings from consistent terminology, standardized instructions of patient’s test behaviors to provoke the respective PFM component and with well-matched diagnostic equipment.
Question: 1) How might this study affect your interpretation of future studies on SUI? 

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